1、 Cause:
1. Unreasonable water change: the feeding water of goldfish tank is changed too frequently in the weather of sunlight shortage, which seriously stimulates the endocrine function of goldfish body surface cells, leading to the decay of soft tissue of tail fin;
2. The water is not changed in time: due to the aging of water quality and too strong light, the fin membranes are full of bubbles, and the water is not changed and drained in time, leading to the rupture and decay of the fin membranes, leading to bacterial infection;
3. Poor water quality: the main reason is that the water quality changes rapidly, the fish body is not adapted to it, causing endocrine disorder, which over time causes the soft tissue of each fin to rot, and finally infected by bacteria;
2、 Prevention and treatment:
1. Reasonable water change: timely and reasonable replacement or adjustment of feed water with poor quality can effectively inhibit the occurrence and spread of this disease;
2. For fish suffering from fin rot disease, dissolve 1 g of furacilin or furazolidone in 10 kg water and soak for 20 minutes. Or choose low concentration dosage for sprinkling, which can gradually restore the growth and development of each fin;
3. Put 50g of fine salt in every cubic meter of water, and use it for two to three times, which can play a role in sterilization;
4. Careful feeding: Careful feeding with constant water temperature above 20 ℃ can make the decayed soft tissues of each fin grow and develop completely again. During this period, animal bait fish and insects must be fed more to promote the growth of tail fin.